Fifty-two years ago today, the first human being left Earth, and we began our journey into outer space. But back in 1961, we didn't really know how far outer space stretched, or where all the matter and energy in the Universe came from.

Image credit: NASA, 1962.

That all changed with the discovery of the Cosmic Microwave Background (by Penzias and Wilson, with the Horn Antenna, above), and subsequent measurements that led us to the Big Bang picture of the Universe. Beginning from a hot, dense state the Universe expanded and cooled, forming baryons, light nuclei, neutral atoms, and finally stars, galaxies, clusters and superclusters of matter, where finally human beings formed on our little world, and looked out -- and back -- into the Universe.

But this doesn't explain everything, at least, not on its own. For example:

The Universe could have had any amount of spatial curvature, positive or negative, of any magnitude. But it appears to be completely, arbitrarily spatially flat. When the Universe was a few minutes old, that means it was flat to one part in 1051.

Different regions of space in opposite directions, given a finite age of the Universe, haven't had sufficient time to exchange photons or any other form of information. How, then, is it that every different direction on the sky -- every causally disconnected region -- has the same average temperature and the same average energy density?

If we brought the Universe back in time, arbitrarily far, then according to the Big Bang, it should have been arbitrarily high in energy. Where, then, are all the high-energy relics of the early Universe, like magnetic monopoles?

Original image source unknown.

All of these problems could simply just be the way the Universe is, of course. We get one Universe that we can see and access, and -- as bewildering as it might seem -- not every question we have about it is going to be answerable. There are a finite number of particles, and hence a finite amount of information, in the Universe, and the clues to answer all our questions might not be accessible to us.

But there was a brilliant idea thrown out there by Alan Guth in late 1979/early 1980, which is that you can't extrapolate arbitrarily far back in the history of the Universe. Not to arbitrarily early times, not to arbitrarily high energies. Instead, before you could describe the Universe as hot, dense, expanding and cooling -- i.e., before the Universe could be described by the Big Bang model -- there was a period where it was dominated by the energy inherent to spacetime itself, and it expanded exponentially.

This period of exponential expansion -- known as cosmic inflation -- would basically force the Universe to be flat. Not necessarily truly flat, as it could either be positively curved (like a hypersphere) or negatively curved (like a hyper-saddle), but flat enough so that, from our perspective, it's indistinguishable from flat. Just as panel D above (or the Earth, when you look out your window) appears flat, so the entire observable Universe would appear flat to us.

This also allows the Universe to be the same temperature and energy density everywhere, as well, since a tiny region that expanded exponentially became the spacetime that contains the entire Universe! And -- so long as the exponential expansion lasted at least some 10-30something seconds -- every direction in our Universe would have the same average energy and temperature properties.

That means we had to go from a "false vacuum" state, where there was lots of energy inherent in space itself (which is what would cause the exponential expansion), to a state where the energy of empty space was much lower.

Of course, energy is conserved in this Universe, as best as we can tell, so it has to go somewhere. And where did all of that energy inherent to spacetime go?

Into matter and radiation, of course! So all of that field energy gets dumped into the particles we know (in a process called cosmic reheating), at a temperature that's low enough that no magnetic monopoles get created. In fact, we can place an upper limit on the temperature of the Universe after inflation has ended, and it's something like 0.1% of the Planck energy, which may well be below both the String and Grand-Unified-Theory energy scales, even if they are relevant to our Universe.

This is still a Universe governed by quantum laws, and that means quantum fluctuations happened even during inflation. But rather than being confined to one region of spacetime, because it's expanding exponentially, these fluctuations get stretched across the entire observable Universe!

This means that today, we should see a spectrum of fluctuations that's nearly scale invariant, but slightly tilted (e.g., slightly less than ns = 1), that has a very tiny roll (on the order of 0.008), and that should be of a magnitude that's a few parts in a hundred-thousand.

It must lead to a new prediction of an observable phenomena which can go out and be tested.

And there it is. Inflation happened, gave the seeds for structure in an otherwise uniform Universe, and then created a bath of matter and radiation in almost perfect (but, importantly, not quite), almost isotropic, almost homogeneous way. And it sets up everything our Universe needs for the Big Bang.

Once that happens, your Universe begins cooling as it expands. Now the radiation is free to have its wavelengths stretched as the Universe expands, the volume of the Universe increases even though the number of matter particles stays constant, and, eventually, gravity does its thing. Over time, the great cosmic structures we've come to discover form, and that's our Universe!

So yes, the Universe was once, in the distant past, dominated by energy inherent to spacetime itself. When this period ended, the Universe could then (and only then) be described by the Big Bang, which is where all the matter and energy in our entire Universe as we know it comes into being. And now, that the Universe has diluted -- or expanded and cooled -- so severely, we can finally see that there's still a little bit of energy inherent to spacetime itself left: that's dark energy!

We don't understand all the caveats of inflation, or of dark energy, for that matter, including whether or not they're related. But just a generation ago, we didn't know anything at all about the energy inherent to spacetime, and now we know it to be an integral part of our Universe's history! So when we say the Universe "Started With A Bang," that's just ourobservable Universe, and all the matter and energy in it. But something was before: empty spacetime, expanding exponentially. In physics, that's also known as nothing, and it's where everything came from, and where everything will return to in the future. Let's never stop working to understand it a little better.

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Great article as always, but I'd wish you'd touch on the over abundance of energy inherent to spacetime itself. I agree that energy is responsible for the effects attributed to dark energy, but there is 120 orders of magnitude to much energy in spacetime. If it were as straight forward as that energy being dark energy, the universe would have blown itself into oblivion in the first few moments of existence.

Of course I have my favorite crack-pot theories as to how to reconcile the issue, but would appreciate greatly if you'd do a piece on what main stream science believes on the issue, or as a minimum mentioned there is an over abundance problem so that people don't read your blog thinking they now understand something that may not yet be understood.

Ethan, sorry to go all fundamental physics on you, but it's the energy inherent to space itself, not spacetime. Spacetime is a mathematical space, and it's static. You can depict the spacetime of the universe as an inverted cone, but space is then a flat slice through it, and it's space that's expanding over time, not spacetime. I said flat deliberately because because curved space is associated with electromagnetism*. Curved spacetime is associated with gravity and cosmology. The universe features curved spacetime because space is expanding, hence a light ray will trace a curved path. But without the expansion, it doesn't. Hence there is no overall gravity to cause a "big crunch". See http://iopscience.iop.org/0256-307X/25/5/014 re the link between inhomogeneous space and curved spacetime.

The onset of the dimming of the universe coincides with the onset of cosmic acceleration. Kepler thought that it was the sun's light and not its mass that made the planets orbit the sun. I star light attractive? Could its dimming cause cosmic acceleration. I am getting a 7 pound test mass to lose 99% of its weight using spreading heat and its absence coldness. These experiments suggest that if is spreading light falling on cold mass is really what is responsible for the gravitational force? When the aether could not be found, a paradigm shift was adopted to deal with the anomaly. We have had two glaring anomalies of flat rotation curves and cosmic acceleration. So what is called for is a paradigm shift that has now been substantiated by simple table top experiments that cost a minuscule fraction of the billions that have been spent on the putative dark matter and dark energy concepts. http://www.kickstarter.com/projects/1887069385/a-silent-anti-gravity-de… .

Einstein reintroduced an "aether", see wiki and note the comment by physics Nobel laureate Robert B Laughlin: http://en.wikipedia.org/wiki/Aether_theories#General_relativity . Also see http://tomwhyntie.wordpress.com/category/uncategorized/ for mention of ex-CERN physicist John Ellis referring to the Higgs field as a kind of relativistic aether, and of course Einstein's 1920 Leyden Address at http://www.zionism-israel.com/Albert_Einstein/Albert_Einstein_Ether_Rel… . Search arXiv too. I'm not forn of the word aether myself, I think it's better to call it space, but appreciate that since it sustains waves and fields, it isn't nothing. See Einstein's 1929 presentation on the history of field theory for that. It's at http://www.rain.org/~karpeles/einsteindis.html . Pay careful attention to this: "It can, however, scarcely be imagined that empty space has conditions or states of two essentially different kinds, and it is natural to suspect that this only appears to be so because the structure of the physical continuum is not completely described by the Riemannian metric". You betchya. Personally I think Oppenheimer's original "frozen star" black hole interpretation is right, and that the early universe wasn't entirely different. If everything within the universe was "frozen" during the initial expansion, that expansion would seem to be very very fast in comparison. Hence the inverted-cone spacetime depiction looks more flat-bottomed, and you've taken the first step from a Martini glass to a flared wine glass.

Wow: spacetime can't change because it already includes time. It's an "all-times" mathematical model, a block universe in which you can draw worldlines and light cones, but in which nothing actually moves.

Being that Oppenheimer's Frozen Star was related to external observers, are you suggesting the initial expansion was a straight martini glass cone but only appears to us as a wine glass due to our external observer point of view?

Re "the caveats of inflation" paper the last link refers to, why do I get the feeling that Steinhardt (who is a decided author of ekpyrotic and cyclic models of the universe) doesn't really like inflation? =D

Unless I missed something, Steinhardt et al tries to have it both ways. The paper is arguing that the unlikely ("finetuned") aspects of the universe such as the parameter values of the standard model of particles or the low cosmological constant shouldn't be taken as evidence for an anthropic selection on a natural eternal inflation multiverse. But it is also arguing that the likely aspects (basic tests of inflation) should be taken as evidence against inflation.

The industry of finding problems with initial and constraint (choice of measure, how to couple the potential energy to heat the universe, et cetera) conditions of inflation is an old one. The complaint that it makes the initial conditions less likely seems familiar.

One simple solution is a Susskind eternal universe that when we go backward we never run up against Planck scales. Then all the papers problems go away AFAIU (with a suitable Hubble parameter for the inflationary phase, I gather from Steinhardt's et al paper). In that sense one could see the paper as suggesting eternal inflation.

Steinhardt et al would see that as picking an unlikely initial condition. But I am struck by the likeness between the "new inflation" 1D potential model and the 2D Mexican hat potential of the Higgs field. No one seems to take Higgs as less likely because the system starts out on top of the hat in a finetuned, unfavorable part of the potential. Of course I don't understand the technical details, but the analogy suggests that selection bias suffice to predict both kind of behavior.

Finally, thanks for seeing some reactions to Planck! Another type of reaction is found here, where inflation is accepted as humdrum: [the deviation from scale invariance to match predictions] is "just one number".

The analogy I can think of is how general relativity was tested against Mercury's orbit early on, but it was "just one number". Accordingly GR was seen as a curiosity until black holes and their physics heated up the field.

But I find this response curious in turn. As seen in the link inflation makes 5 specific predictions. And Planck tests the deviation from scale invariance to 7 sigma, and the remainder to above 3 I think. So if these were independent random numbers, it would be a very unlikely outcome compared to the Mercury observation that was barely legit!

And the series of articles points out how inflation makes non-trivial, "black hole like" predictions. AFAIU it predicts "the particle content of the early universe" (the plateau of slow roll inflation), and "the sound speed of the early universe" (sound speed close to the universal speed limit).

@Denier: You must distinguish between spacetime, which energy density in a Friedmann universe as ours is zero, and the vacuum, which energy density is proposed to be that of the cosmological constant of the inflationary standard cosmology.

Your "120 orders of magnitude to much energy in spacetime" is the 120 orders of magnitude too much energy of the vacuum in naive predictions from the zero-point energy of fields. So you have it backwards, we don't see that and there is no problem with what is seen.

@John Duffield: As people noted, in some ways GR makes your claim of static spacetime problematic. Even so, marrying it with QM and specifically decoherence shows how non-trivial spacetime is.

Consider this from a non-block local reference frame: We can make a cosmological clock that advances according to CBM measurements (say). But there will be local deviations due to entanglement, where part of the lightcone will be undecided until observations are done.

These local "inverted spikes" of the advancing cosmological clock will be decided sooner or later. (Most likely sooner, since systems are inherently sensitive to decoherence from the environment.) And the lightcones will smooth out the clock front and catch up to it due to the 10^10 times slower cosmological expansion rate. This works out to the cosmological horizon where the signals are diluted into oblivion, so no inconsistencies what I can see.

So, how do we reconcile such a QM+GR semiclassical time process with a block universe? I don't think we can.

Einstein's notion that mass can warp space-time cannot explain why a 7 pound test mass can lose 99% of its weight. If dark energy and dark matter can not be comprehended by any other way than their gravitational effect, than this mysterious notion that mass can warp space time fails to explain gravitational phenomena. If a theory disagrees with an experimental result, than that theory should be rejected even if that theory has been around for a long time and accepted by a majority of scientists. The phases of Venus that could be seen through Galileo's telescope finally downed the Ptolemaic system. Go ahead ignore my "paradigm shifting" experimental results. General Relativity is losing its grip on scientist Someone is bound to repeat my simple experiments and then all this concern with how space time can explain this and that will be as important as Ptolemaic epicycles and equants.

It's deeper than just "mass attracts mass" or that mass warps spacetime (both true). What about the "relativity of inertia" notion, where Einstein sezs that masses piled up together gain inertia (mass)? Does anyone know if this can be calculated? I saw the Discorsi Scientific speak on this point, but it's not yet disclosed how to do this.

Denier: No. The Martini glass was just a starting-point illustration. See Phil Plait likening dark energy to pressure here: http://www.slate.com/blogs/bad_astronomy/2013/03/21/age_of_the_universe… . The expansion starts fast, the pressure drops, the expansion slows down. But any "frozen star" internal observers would claim that the initial expansion was very very fast.

Torbjörn: It isn’t my claim, google on “spacetime is static”. Perhaps I can illustrate by throwing a red ball across a gedanken room. You film it with an old cine camera, then develop the film and cut it up into individual frames. Then you stack the frames into a block. The red streak within the block represents the ball at all times. In no sense does the ball move through the block. Ditto for light. I’d say to to marry GR with QM and reconcile QM+GR semiclassical time with a block universe, one takes a Lundeen/Steinberg view that wavefunction is real and can be measured in a lab, whilst a lightcone is an abstract thing. This involves taking a step away from the Copenhagen Interpretation and Consistent Histories along with spooky action at a distance. It’s a big subject in its own right I'm afraid, too big for me to go into here.

It seems to me that Casimir plates might have a couple of practical applications:

1) Means of measurement of very small masses in low to zero gravity, such as when conducting materials science experiments aboard a space station.

2) Inertial guidance system for robotic spacecraft maneuvering near the surface of a planet or its satellite, to conduct mapping of the surface.

In each case, the plates are initially calibrated to balance between the force acting to press them together, and the force acting to keep them apart. For the inertial guidance system, three sets of plates would be used, oriented on the X, Y, and Z axes respectively.

Is this even remotely consistent with accepted theories, or is it utter crap, or somewhere in between?

G: Sorry to chime in again, but the Casimir effect is very weak. IMHO you'd be better off measuring the fine structure constant via the quantum Hall effect. The FSC is a "running" constant, see http://physics.nist.gov/cuu/Constants/alpha.html and http://link.springer.com/chapter/10.1007%2F3-540-40988-2_19 . People have speculated that the FSC varies with gravitational potential for a while. Some take the view that such would invalidate the equivalence principle and GR, but I don't share that view myself. Also see Webb's http://arxiv.org/abs/1008.3907 re variations in the FSC, along with Milgrom's http://arxiv.org/abs/0912.2678 for mention of "modifying the ‘elasticity’ of spacetime (except perhaps its strength), as is done in f (R) theories and the like". The FSC relates to the coupling constants and the strong force and the bag model and so tension. IMHO space expands so the strong-force tension weakens and the pressure runs away a bit like drooping Silly Putty. Hence the flare on the wineglass.

Wow: Einstein didn't say "no such thing exists". See his 1920 Leyden Address at http://www.zionism-israel.com/Albert_Einstein/Albert_Einstein_Ether_Rel… where he said: "Recapitulating, we may say that according to the general theory of relativity space is endowed with physical qualities; in this sense, therefore, there exists an ether..." Then see his 1929 presentation on the history of field theory at http://www.rain.org/~karpeles/einsteindis.html and note where he said: "It can, however, scarcely be imagined that empty space has conditions or states of two essentially different kinds…” A field is some"state of space, nothing more, and space isn't nothing. Again see the GR section of the wiki aether theories article and see what Robert Laughlin said: "It is ironic that Einstein's most creative work, the general theory of relativity, should boil down to conceptualizing space as a medium when his original premise [in special relativity] was that no such medium existed..." And see above where I referred to the quantum Hall effect. Robert Laughlin is no dummy, he got a share in the 1998 Nobel Prize for the fractional quantum Hall effect. You might give Pete a pointer, but this ought to give you a pointer too. Pete dismisses Einstein, so do you. Don't.

John #23
You say take a look.
Have you taken a look at any of those papers? I don't think so.

The first one has a nice title but is totally unreadable.
So next time, please explain (in your own words) why a paper to which you point has a worthy (even if far fetched) idea.

Because, if you can't give the one paragraph summary of why it is important to you. Well, you devalue your discussion as political jargon "aether" and "Einstein"; without a single scientific ideas expressed.

Further, this blog is not the place to discuss OR debate your personal hypotheses (or mine either).

When I might personally say that I have a problem with the interpretations of "dark energy" and "dark matter". I also clarify that I have no problem with the body of astrophysical observations that are represented in the phrase "dark matter observations" and "dark energy observations"; nor do I have any problem understanding the hypotheses in the "body of theories" covering these topics. So I haven't really said to much; I've just emphasized that scientific consensus has not been reached. Whoopee.

Yeah, whoopee. But sometimes that's an important point for me to make. And yeah, whoopie.

However regarding the "aether", I have no idea what "body of current physics observations" might possibly be represented by the term "aether"; nor even what "body of current physics theory" might possibly be represented by the term "aether" or "relativistic aether."

Look up aether on wikipedia. Notice that there is no current physical definition of aether. That does not mean that the old classical idea is completely without current merit. Nor does it mean that the papers that you point to in arxiv are without merit.

But it does mean that you are pointing to an ambiquity. And your paragraphs do not clarify any of those papers; your paragraphs only further the ambiguity by using scientific sounding terms as political slogans and catch phrases without adding any physical insight (that I can understand).

In my opinion, you are talking utter nonsense.

Hmm, let me have a try at this relativistic aether nonsense.

WARNING, I AM ABOUT TO TRY TO TALK COMPLETE NONSENSE.
"The aether is really a relativistic aether but it includes the quantum vacuum too and thus it in fact is a quantum field theory. Of course the mathematics of a zero point energy relativistic aether is very difficult; mostly because the concepts are difficult for all but a few brilliant scientist to understand and very difficult to put in appropriate mathematical formulation. Nevertheless the relativistic aether is a beautiful hopeful physical insight whose mathematical formulation will clarify our understanding of such diverse phenomenon as dark matter and dark energy. It will must surely also explain the baryon asymmetry of the universe and why three famililies of quarks and leptons are absolutely necessary to a complete physical understanding of the universe and other longstanding physical paradoxes."
DISCLAIMER ANYTHING THAT I HAVE JUST SAID THAT MAKES ANY PHYSICAL SENSE AT ALL IS COMPLETELY UNINTENTIONAL. THE MEANING OF THIS PARAGRAPH IS JUST UTTER NONSENSE.
How'd I do? Did I catch your meaning John #23?

You could fool my mother or my friend Bob any day of the week with your nonsense; but you can't fool Wow.

1) Yes, the Casimir force is extremely weak, and it's also pervasive and (at risk of another foot-in-mouth maneuver but nonetheless) it ought to be uniform throughout the universe. That was the combination of properties that struck me as useful for both the "weighing" application and the "inertial guidance / mapping" application. Now it would appear I've landed in the midst of an unrelated controversy, so I'll put the whole idea on a "skeptical hold" until I fill in more of the obvious large gaps in my knowledge.

2) Other: the Higgs and false-vacuum states:

I recall reading that one of the implications of the measured value of the Higgs particle at 127 GeV, is that we may presently be residing in a false vacuum state. Yet, per Ethan above, the end of the exponential expansion phase of the universe occurred in a shift from a false vacuum state to a true vacuum condition "where the energy of empty space was much lower."

Question: which is correct? Is the universe presently in a false vacuum or a true vacuum? Or could it be that the end of exponential expansion was a transition from one false vacuum state to another of lower ambient energy, with the true vacuum as yet unrealized? (And, sticking my neck out into "this may be ridiculous" territory again, could it be reasonable to suggest that there are a number of metastable states or plateaus or valleys, along the way from the early state of the universe to some final state with substantially different physics?)

Why this interests me: The idea that the universe we observe has a singular existence with a discrete birth, finite lifespan, and ultimate heat-death, strikes me as implying that we inhabit a privileged position somewhere in the middle of that lifespan. Yet I'm skeptical of "privileged positions," and am more inclined toward interpretations in which our own existence is in no way privileged: such as that the observable universe is only 1 / a very large N of universes, even if there is no connectivity or information transfer whatsoever between them.

3) A few other unrelated questions (for now, heh;-)

Is Brownian motion sufficient for measurement of time? That is, if all you have in a given system is an isothermal condition with Brownian motion or similar random movement without any overall direction, can you make a measurement of time from within that system? And if not, what happens to the time dimension? Does it drop out of the system entirely? What would that imply for the spatial dimensions in that system?

The idea that the universe we observe has a singular existence with a discrete birth, finite lifespan, and ultimate heat-death, strikes me as implying that we inhabit a privileged position somewhere in the middle of that lifespan.

In some ways yes, in some ways no. We're 13 billion years into a universe expected to last for (IIRC) many many trillions of years - nowhere near the temporal middle. It would probably be more correct to say that life formed almost as fast as it could, given the need for stars, planets, a mix of heavy elements etc. Sure, we could've shown up maybe a few billion years earlier, but we still arrived in the first 0-1% of the universe's lifetime.

So that's the "no, not privileged" answer. Nothing more than normal physics and statistics is needed to explain a stochastic event that happens just about as fast as it can happen in a very large sample base (i.e. lots of potential planets after gen-2 star formation). That's just a lottery where someone wins every week because there were so many tickets sold.

The "yes, privileged" answer is that we live in an era where what we can observe gives us lots of information about what happened earlier. From what I've read here and though Phil Plait, that will not always be the case. In a few hundred billion or trillion years (closer to the actual temporal middle), the alien astronomers and philosophers will be SOL when it comes to using empiricism to figure out how the universe started.

Agreed, life develops quickly wherever conditions are appropriate, and in all likelihood the universe is infested with simple life, though complex life is progressively more rare. (This is a problem for space colonization: any suitably habitable planet will have to be treated as a red hot biohazard until proven otherwise.)

Per Wikipedia "timeline of the far future" (yes you're welcome to laugh at my layperson's use of laypersons' sources, but none the less....) 10 ^ 14 years = the point at which star formation ceases, which I would consider the beginning of the end as far as life is concerned, but by no means the end as far as the universe itself is concerned. For that we need to go to somewhere between 1.7 x 10 ^ 106 years and 10 ^ 10 ^ 120 years for the final energy state to be reached (presumably isothermal and maximally entropic).

However, as our elected representatives have lately taught us to routinely conceptualize trillions (of dollars, rather than years, but it's the thought that counts), going from there to numbers best rendered in exponents atop exponents is a relatively straightforward conceptual leap (yeah right;-). In any case, a finite lifespan of gazillions of years is still a finite life of a singular event. Seen from the perspective of eternity (infinite time), it's still "one lifetime" of a universe.

So here's a potentially interesting scenario for possible use in fiction:

The time is "far in the future," when astronomers and philosophers will see a local universe that is far more limited than our own: a night sky dim with relatively few stars, and a telescopic view that's little better.

Absent the empirical view, they will have to rely on "ancient stories" from people who claimed to know much more and see much more.

I would predict that under those conditions, there would be a rise of diverse nonstandard cosmologies, and a rise of religion as the primary means of interpreting the universe and the place of intelligent life in it. None of these will be able to point directly to present observables as their foundation and claim of correctness.

Interstellar civilizations that once flourished and communicated freely (though subject to c delay) will find themselves torn apart, unable to communicate at all. Some of their member planets will likely regress to permanent dark ages.

It will be a radically different existence from what we know now, minus the irreplaceable natural beauty of direct observation of the cosmos. Something else will take its place, perhaps a sense of natural beauty much closer to home, or something as-yet-unimaginable in the arts or philosophy.

Between now and then, there's plenty of time for interstellar colonization, and no excuse for not proceeding in that direction.

G: the Casimir force ought to be uniform in a perfectly homogeneous universe. But as soon as you include gravitational fields, it won’t be. You’re using the plates to measure vacuum energy density/pressure, and when you look at the Einstein field equations, there’s energy density and pressure. See for example Dr A G Polnarev’s course notes at http://www.maths.qmul.ac.uk/~agp/MTH6123/co_notes20_10.pdf

Yes, best steer clear of aether controversy.

I can’t answer your question re Higgs and false-vacuum / true-vacuum states. I’d say it’s safe to say that vacuum can have more than one state and that this can vary smoothly over space and/or time. But as to valleys and metastable states, I don’t know. Can I add that I think you should be more skeptical of the multiverse than “privileged position”, which is shaky anyway. We are where we are.

Re time, I’d say that if there is no motion and no change of any kind, then there is no time. This then implies that the spatial dimensions of the system are undefined. And if you're looking for a bit of heh, note that the gravastar, which is hypothetical but not entirely unlike the frozen star I mentioned earlier, features a central region “called a ‘gravitational vacuum’, because it is a void in the fabric of space and time.” And for a cherry on top, it features a Bose-Einstein condensate too. Check out the Bosenova.

That science falls prey to "idiots (in need of) arsed mollycoddling"; is in part sciences' own fault.

Science builds models that DESCRIBE various aspects of the universe. (here I am referring to mathematical models). But sciences' dirty little secret is that very few mathematical models are very good PREDICTIVE models. e.g. of the 17 phases of water, all of them are DESCRIPTIVELY modeled very well; but none of those 17 phases of water were predicted. http://upload.wikimedia.org/wikipedia/commons/0/08/Phase_diagram_of_wat…

What this means is that though we now have more data and more variables (e.g. about water); we have not improved our ability to predict (e.g. the 18th phase of water).

And yet scientists(e.g. Ethan Siegel) insist upon PREDICITING all sorts of things with models that are best viewed as having mostly DESCRIPTIVE value (regardless of mathematical complexity).

In my view, it is best to view many models of Inflation, Dark Energy, and the Physics of Spacetime and such as excellent DESCRIPTIVE models but quite un-PREDICTIVE models.

The art of science is easy to acknowledge in the insights of an Einstein or Witten.

But it is not so easy to acknowledge in the failure of insight and models to predict dark energy or dark matter, here or there. Scientist (and not just AMS dark matter scientist whose $2 billion space based particle detector has NOT found something) hype the interpretation that PREDICTIVELY their science is on a collision course with the discovery of the dark matter particle (or whatever).

G: I clean forgot that measuring vacuum fluctuations isn't the same as measuring vacuum energy. It's a bit like measuring ripples on the sea as opposed to measuring its depth. Vacuum fluctuations aren't the same thing as virtual photons either. See this old 1973 paper http://prd.aps.org/abstract/PRD/v7/i6/p1668_1 where you can read "the identity of these evanescent waves with virtual photons is established". The evanescent wave is a standing wave, and isn't the same thing as vacuum fluctuations.

I see on the "weekend diversion" page, that Ethan say: "Some people do come here curious about the Universe, but with some very deep misconceptions about how things work. People with this mindset are often willing to change their minds if the right evidence comes along."

Go back and read the first paragraph in my comment #28 where I explained how I got the "casimir weighing / mapping tech" idea in the first place, and closed with "...I’ll put the whole idea on a “skeptical hold” until I fill in more of the obvious large gaps in my knowledge." For that matter, in my original comment at #24, I close with "Is this even remotely consistent with accepted theories, or is it utter crap, or somewhere in between?"

Seems to me that's exactly what Ethan is talking about. To be very clear about this: I'm not attached to my hypotheses & speculations, and the reason I bring them up here in the first place is to get them subjected to strict scrutiny. But your remark at #36 is not that: it's a pure ad-hominem, verging on name-calling: coincidentally right at the bottom of the pretty rainbow-colored triangle in "weekend diversion," with the caption "Paul Graham's hierarchy of disagreement." Perhaps you missed that triangle because it's rainbow-colored and anything with those colors is obviously pseudoscientific nonsense?

BTW, "synchromesh" is a term for a type of automotive manual transmission in which components are designed to align when shifting, to avoid "grinding the gears." If I'm not mistaken it was a brand name or proprietary term at one point.

As for whether this universe is "the one and only" in all of existence, that's still an open question, isn't it? I'm skeptical about Everett but intrigued with (and tending toward skepticism about) other "multiverse" models. Frankly I'm inclined toward some kind of oscillatory model simply on the basis that it's an extension of "non-privileged position," and yes I'm also aware of the thermodynamic issues with some of the oscillatory models, but they seem to be less extreme than what's required by Everett (that is, there could very well be a loss of energy at each oscillation, but to my mind that's less problematic than the question of where the energy comes from to fork some part of the universe at every wave-function collapse).

Speculating about fiction set in a far future where the absence of empirical observations leads to a rise in nonstandard cosmologies and religious interpretations, does not qualify as pseudoscience either, any more than using something from Star Trek as an analogy. I for one would hate to live in a world where all of today's science is written off because it's "ancient" and some new inquisition arises to enforce whatever kind of supernatural dogma happens to be in power at the time.

Anyway, if you'd like to argue the arguement rather than sling ad-homs, feel free, I'm all ears.

And if Ethan says all of this is a digression, that's his judgement call, and his right to tell us to cut it out.

Wow @ #39, you're indulging in an attempt at mind-reading and armchair psychoanalysis, and like most such attempts, it fails.

Apparently you missed paragraph 3 where I pointed out that I asked bluntly if my original speculation was "utter crap" quote unquote. Paragraph 6 _admits my biases_, which is _not_ the same thing as _arguing for_ them or _defending them_. (And if someone pops in here and admits that they're religious, do you accuse them of attempting to proselytize for theism?)

So far nobody has asked any questions about where I got any of the original stuff from, nor would I have expected any such questions, because how I got there is not particularly pertinent to whether any of it is any good or, as I said, "utter crap." (In any case I have no stake in whether casimir plates will or won't work for e.g. inertial guidance systems: I don't have the facilities to build a test model much less profit from it in any way. It was an interesting idea and that's all, and apparently you also missed the places where I said I was putting it on skeptical hold: and this assertion is not a _defense_ either, much less "part of [my] self-image.")

Frankly you're engaging in confirmation bias yourself, where any time I say "I wasn't doing X, I was doing Y" is further proof that I was doing X. Puh-leeze. That sort of thing is appropriate to sports bars, not science blogs.

I'm an engineer. I'm used to testing every design I come up with and finding out quickly whether it does or doesn't work: "when Should competes with Is, Is wins every time." The feedback is rapid and unequivocal, and leaves no room for getting attached to "Shoulds." Troubleshooting technical systems of any kind is an exercise in empirical method: observe, hypothesize, test, refine. It's also universal in the repair trades including plumbing, electrical, electronics, and auto mechanics.

Your #39 is a textbook case of what drives laypeople away from posting in places like this. If that's your goal, by all means keep it up. And if you're serious about mind-reading, I'm thinking of an animal: tell us which one.

I’m skeptical about Everett but intrigued with (and tending toward skepticism about) other “multiverse” models. Frankly I’m inclined toward some kind of oscillatory model simply on the basis that it’s an extension of “non-privileged position,”

IANA cosmologist, but from Ethan's posts, here's how I undertand the situation (and why the multiverse idea beats the oscillatory idea hands down). Right now our best cosmological theories predict many things. To keep it simple, lets call them things A, B, C, D, and E. When A, B, C, and D predictions have been observed to be true, one is inductively justified in tentatively concluding E is true too, even though it hasn't been directly observed (and with the scientific caveat that one is willing to revise one's belief in E if future evidence shows E not to be true).

E is the multiverse. Our best cosmological theories predict many things that have turned out to be true, AND that the multiverse is out there. Barring some contradictory observation, we should give it tentative support for the moment.

AIUI no such logic holds for the oscillatory model. Its purely a stop-gap idea. We have no direct evidence for either, but where the multiverse idea has some indirect scientific support for it, the oscillatory idea doesn't even have that. The only thing it has going for it is it scratches a materialst philosophical itch not to be privileged.

If one is inclined to be philosophically conservative, one could make a reasonable argument for saying neither idea is well enough supported at this time (for someone to believe it). But if you're going to pick one based on assessment of each idea's relative support, the oscillatory idea should certainly not be preferred, because relatively speaking, its worse off than the multiverse idea.

Maybe you haven't been taught this, and maybe you have and have ignored it, but the term "aether" has a precise meaning relative to the physics of the late 19th to early 20th century, but is no longer a term used in physics because the concept was found to be unnecessary.

To fully grasp the meaning of the term, a bit of history is in order. In the late 19th century, waves were a well-known phenomenon. It was also well known that light was a wave; its wavelength had even been measured by that point. All waves known at that time, other than light, obviously travelled through a medium; sound waves, water waves, etc. It was not known what the nature of light was nor what the medium was that it travelled through.

Maxwell developed the equation that unified and explained a wide range of observations in the fields of electricity and magnetism, and for the first time it was recognized that electricity and magentism were really just manifestations of a single phenomenon. Electromagnetism was born. One of the new insights from Maxwell's equations was that there was the possibility that electromagnetic waves could occur, so long as they propogated at the same speed that light was known to propogate. Obviously, this was too much of a coincidence for physicists to believe that light could be anything other than the very electromagnetic waves that were predicted by Maxwell.

The kicker to all this was that these waves must travel at c, but relative to what reference frame? The aether was proposed as that reference frame. It was to be both the reference frame relative to which light must propogate at the speed c and the medium through which light waves were propogated.

Problems soon arose, however. The earth is moving through this aether, presumably. Therefore, when making measurements of the speed of light, light should travel faster in the direction opposite to the earth's motion through the aether than it does in a direction parallel to this motion. Michelson and Morely conducted an experiment that showed that this difference did not occur; light travelled at exactly the same speed in all directions.

This led to a variety of ad hoc hypotheses, such as the Lorenz length contraction and the idea that there is a stationary boundary layer of aether surrounding everything. It was actually Einstein who put all these to rest, even if he really didn't realize it at that time. His theory of special relativity rests on two postulates: 1. The laws of physics are the same in all reference frames, and 2. The speed of light is the same in all reference frames. Now we no longer need aether as a reference frame for measuring the speed of light. Light has the same speed relative to all reference frames. We also know that light can propogate through the vacuum. Since that's true, why do we need the term "aether"? The term "vacuum" serves just as well, and the notion of "aether" has dropped out of physics.

Please note, that even if Einstein believed in aether, that's irrelevant. That's akin to the creationist argument that Darwin disavowed evolution on his death bed. This is untrue, but even if true, it's irrelevant. The science stands on its own regardless of the beliefs of any individual scientist. I'm sure you think I'm talking sacrelige, but it is possible that even if Einstein believed that aether existed, he could have been wrong.

"Please note, that even if Einstein believed in aether, that’s irrelevant."

He did to begin with, but dropped it after trying damn near everything to keep it.

Note that due to the ALREADY KNOWN electrodynamic effect where a changing electric field will CAUSE a magnetic field (and a changing magnetic field will CAUSE an electric field), there's no need for a photon to have any medium to project itself.

The very fact that a photon is an oscillating electric/magnetic field means it can self-propagate.

Sound waves require a medium because the pressure waves are not the sound itself and do not self-generate without that medium which the rarefaction/compression takes place, or water waves are the result of circular motions in water, the wave again is not the water, nor moving any of the medium in this case (the restoration being geopotential energy, and again, not self-propagating).

"Wow @ #39, you’re indulging in an attempt at mind-reading and armchair psychoanalysis, and like most such attempts, it fails."

G, many who are found out and are in self-denial use the very same assertion to deflect and ignore the accusation.

I gave the features that informed my conclusion (no mind reading required, any more than mind-reading is needed in court cases to prove (or not) guilt).

"Apparently you missed paragraph 3 where I pointed out that I asked bluntly if my original speculation was “utter crap” quote unquote"

No, I saw it.

Apparently, you are talking the talk, but when it comes to walking the walk, you're sitting on your arse.

People are saying your assertions are utter crap.

But you don't accept it.

The currently best known science by those actively looking into this says the assertions are utter crap.

But you don't accept it.

You hug those ideas close to you, and go all "faux Voltair". You know, when the idiot goes all "I'm willing to fight to the death to defend your right to speak" but then goes and complains if that speech happens to be in a public park or in a mall or other institution, where it may be *inconvenient* for some people who don't care.

"Note that due to the ALREADY KNOWN electrodynamic effect where a changing electric field will CAUSE a magnetic field (and a changing magnetic field will CAUSE an electric field), there’s no need for a photon to have any medium to project itself."

That's wrong. The field concerned is the electromagnetic field. E and B aren't two different fields CAUSEd by changing B or E. See section 11.10 of Jackson's Classical Electrodynamics where he says "one should properly speak of the electromagnetic field Fuv rather than E or B separately". An online copy is here: http://archive.org/details/ClassicalElectrodynamics . Also see what Minkowski said towards the back of Space and Time: "In the description of the field caused by the electron itself, then it will appear that the division of the field into electric and magnetic forces is a relative one with respect to the time-axis assumed; the two forces considered together can most vividly be described by a certain analogy to the force-screw in mechanics; the analogy is, however, imperfect." Electromagnetic field interactions result in linear and/or rotational motion. When our test particle moves linearly we speak of an electric field. When it moves in a circular fashion we speak of a magnetic field. But these aren't actual fields, they're forces that result from electromagnetic field interactions, and are commonly described as two "aspects" of the electromagnetic field.

Potential is more fundamental than field. The photon isn't so much an electromagnetic field disturbance as a "pulse" of four-potential. The spatial and time derivates give you the sinusoidal electromagnetic waveforms. They're two aspects of the same thing. They don't cause one another. See
this:

and note this: "we see that the electric field is just the negative gradient (the del operator) of the potential". Check out Jefimenko's equations and read Einstein's 1929 history- of-field-theory presentation here:

Surely if we all stop bickering and work together, we can actually conquer the Milky Way and fort up in time for our collision with Andromeda? Those 'Drommies will be doing the same, and they'll do the same to us if we let them!

Wow is correct.
He doesn't parade his academic credentials; because he doesn't argue his point based on himself or anyone as an authority.

Wow has earned the respect of most of us on this blog because of
1) his solid knowledge in matters of physics, astronomy, etc
2) his willingness argue with psuedoscientist and crackpots to the end. Must of us just stop talking to John Duffield's on this blog. But Wow defends science against there nonsense.

For sure, I do from time to time disagree with Wow out here.
But even then, I know that his understanding of mainstream physics and astronomy is much more correct than mine. I just prefer a minority interpretation, or question the domain of relevance, or have philosophical difference. But I listen and learn and do change my opinion due to Wow clear understanding and willingness to explain.

But John Duffield, in my opinion, everything that you accuse Wow is much better applied to you:
- JD's point is wrong. He has a schoolboy popscience misunderstanding of electromagnetism
- JD dismisses and misrepresents Einstein's meaning like all cranks do
- JD doesn’t know much physics
- JD is not a cosmologists, astronomer, physicist, mathematician. Did you ever take high school physics and calculus?

John Duffield stop wasting everyone's time with your misunderstanding AND YOUR UNWILLINGNESS TO LEARN.

Re. Wow@ 37: moot by way of Eric @ 41, which is the kind of arguement that succeeds, in summary: "given the present state of science, even though observables are scarce, they point toward theory A rather than B, so at this point A is considered more plausible than B." OK, re-evaluate & update, no problem, and no emo dramas needed.

FYI, in an entirely unrelated area, I used to believe that "intuition" was background processing in the cerebral cortex, until I ran across a paper that demonstrated it was basically emotional feedback at the rat-brain level. Humans tend to prefer to believe that their cognitive abilities are unique among animals, but the explanation in the paper was sufficient that it convinced me on the spot. In fact I got a big smile on my face in the way I often do when I discover that one of my favored hypotheses has been refuted: because in my experience, when that happens, it usually turns out that nature is more interesting than we expected.

When seeking to attract bees, honey works much better than vinegar. (And if some flies come in along with the bees, a closely-targeted flyswatter works much better than spraying the whole picnic with insecticide;-)

To that I should also add, the prospect of a multiverse is far more "interesting" in certain ways, than the prospect of an oscillating single universe.

Any kind of empirical support for a multiverse theory, even if indirect, necessarily entails some kind of contact between universes via which causality (or at least information) of some kind is transferrable: even if only as a slight deviation from the predicted characteristics of one or another type of background noise.

If that's true, then sufficient improvements in technology should provide stronger empirical support over time, and this issue (as with the Big Bang and the expanding universe) ought to be possible to resolve conclusively or nearly so.

So the question is, where to look for that?, and what are the keywords for I should be alert, as indications of progress in this area?

Upon inflation, gravitational densities were formed, pulling matter to an embryonic state which resulted in our perception of the observable universe.

The common view is that 'matter' somehow dominated, resulting in what we now live in.

This theory implies that the 'matter' is a residual, minority 'effluent' of the Big Bang.

This idea is not only speculative, but, in my opinion, lazy.

If inflation cased localised densities for matter, then it could, in probability, do the same for anti-matter.

Localised extremes of energy could force matter to condense whilst at the same time cause antimatter to diffuse. The result might be that condensed matter and diffused anti-matter were polarised to such an extent the they could not interact readily.

What if, the balance of condensed matter, and diffused antimatter, thet do not interact due to the differentiation occuring duing inflation

@Kevin Flin #61/62: Your confusion is quite understandable, and due (I think) to the rather loose way in which we particle physicists occasionally use the word "matter."

In the context of the initial (post-inflation) density fluctuations, those would have attracted baryonic matter, anti-matter, and dark matter all equally well -- anything with mass, essentially.
[ One caveat: we do not yet have direct, experimental confirmation that gravity acts on antimatter the same way as matter, but since it has positive total energy, and GR operates on energy, any other result would be rather, um, "unexpected." ]

The asymmetry between matter and antimatter is an observable fact of our universe. Observationally, the baryon/photon ratio is of order 10^-9, not zero. There was a very nice CERN paper done back in 1996 which went through the observational evidence in detail, such that there cannot be any appreciable antimatter within something like 10 megaparsecs of us. If there were large clumps of antimatter in the Universe at large, then we would see continuous, relatively large sources of gamma rays, which we do not see.

As I noted above, gravitational effects would apply identically to matter and antimatter. Similarly, other energy inputs, such as temperature differences, would also apply equally to both (raising the temperature of a matter gas increases its pressure or volume; the same applies to antimatter gas).

We have to start with the speculation that inflation allowed for the formation of a superluminal universe(.Very contentious.) and the presence of particles there(matter,antimatter or tachyons) all of which have mass and associated gravity. It is this gravity that extends to our distant galaxies and produces the effect we call dark energy.

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